1. Field of the Invention
The invention resides in the field of slip casting machines and more particularly relates to a slip casting apparatus comprising a supply tank, a reserve well in communication with said tank, a pump means to pump said slip from said tank through a delivery means to casting molds and having provision for continuously recycling the slip in and out of the supply tank. The same pump is utilized both to deliver slip to casting molds and to recirculate slip within the supply tank, in a manner which eliminate settling and relieves the pump from undue pressure. The well functions to prevent the formation of air bubbles.
2. Description of the Prior Art
Slip casting machines which support molds above a supply tank which catches excess slip poured from molds in the tank are well known in the prior art. They are usually accompanied by a mechanical agitator used to mix continuously the slip, i.e., liquid clay in the form of a slurry, to maintain a homogeneous consistency and to prevent premature drying. Mechanical agitators have the disadvantage of introducing air bubbles into the slip since they create a vortex at the surface of the slip and generate a certain amount of turbulence and churning in the vicinity of their action. They have the further disadvantage of having relatively short useful lives and require frequent maintenance and repair. The density of liquid slip places an extremely heavy load on the agitator motor and sometimes requires a second motor to drive the pump.
Furthermore, prior art machines which churn or agitate liquid slip frequently cause air bubbles to form in the slip. Air bubbles should be avoided in slip casting since they result in an uneven surface or thickness of the molded greenware and, if internal in the body of the finished article, result in cracks and other imperfections in the finished article upon firing.
The slip casting apparatus of the present invention is designed to avoid the above-mentioned deficiencies in prior art machines. The use of recirculation system eliminates the need for a mechanical agitator and in most cases the need for a separate motor to drive the agitator. The recirculation system prevents the liquid slip from settling, drying or otherwise becoming non-homogeneous in the supply tank, while at the same time minimizing the occurrence of air bubbles in the liquid slip. The reserve well in communication with the supply tank also serves to eliminate air bubbles in the slip as will be described below.
The inventor knows of no other apparatus based on this principle in the field of slip casting. Furthermore, the slip casting apparatus of the present invention is mechanically and functionally simpler than the prior art devices, is less expensive to manufacture and requires less maintenance and repair. Additionally, it is easily moveable despite the capacity of the supply tank, and it utilizes the full area of the mold support rack.
The apparatus of the present invention may also be utilized for pumping, recirculating and pouring or casting other liquids which have characteristic properties similar to those of liquid slip.